Interpretive Summary: In 1995-1996, much attention was focused on Streptococcus iniae, a Gram positive bacteria, in North America because of the reported potential for human infection due to puncture wounds received while preparing tilapia for cooking. Because of the perceived risk to the public, the prevalence of this bacteria in tilapia, hybrid striped bass and channel catfish from farms in the United States was determined. Streptococcus iniae was isolated at a low rate from tilapia and hybrid striped bass (3.82 and 7.23%, respectively). No S. iniae was isolated from channel catfish that were sampled. Prevalence in market sized tilapia was found to be 18-50 fold lower than the published report of fish sampled in Canada from suppliers or retail outlets. The results of this study do not support the contention that exposure to S. iniae is common from cultured fish. Presently, no cases of S. iniae infection have been reported in the U.S. population and human infection has not resulted from eating fish.

Technical Abstract:
In 1995-1996, much attention was focused on Streptococcus iniae in North America because of the reported potential for human infection due to puncture wounds received while preparing tilapia for cooking. Because of the perceived risk by the public, the prevalence of S. iniae in tilapia (Oreochromis spp.), hybrid striped bass (Morone chrysops X M. saxatilis) and channel catfish (Ictalurus punctatus) from farms in the United States was determined. Streptococcus iniae was not isolated from market size channel catfish. Prevalence in tilapia and hybrid striped bass was 3.82 and 7.23%, respectively. Prevalence by farm ranged from 0.0-27.4% for tilapia and 0.0-21.6% for hybrid striped bass. In tilapia, prevalence was lowest in market size and nursery fish (1.67 and 0.88%, respectively) with an increase in prevalence for the production group (7.96%). For hybrid striped bass, the prevalence was lowest in nursery and market size fish (3.12 and 2.12%, respectively) and highest in production fish (9.56%). Prevalence in market sized tilapia and hybrid striped bass was found to be 18 to 50 fold lower than the published report from Canada in tilapia from suppliers or retail outlets. Results of the present study do not support the contention that exposure to S. iniae is common from cultured fish. Presently, no cases of S. iniae infection which occurred in Canda have been reported in the U.S. population of individuals of Asian decent.